A new world record has been confirmed for the longest lightning flash ever recorded – stretching out an extraordinary 829 kilometers (515 miles) across the Southern US during an October 2017 thunderstorm.

The lightning megaflash spanned the US Great Plains from eastern Texas to near Kansas City, about equal to the distance between Paris and Venice, the World Meteorological Organization (WMO) certified Thursday.

"It would take a car about eight to nine hours and a commercial plane at least 90 minutes to cover that distance," the WMO said in a statement.

"Lightning is a source of wonder but also a major hazard that claims many lives around the world every year and is therefore one of the priorities for the international Early Warnings for All initiative," said Celeste Saulo, who heads the UN agency.

"These new findings highlight important public safety concerns about electrified clouds, which can produce flashes that travel extremely large distances and have a major impact on the aviation sector and can spark wildfires."

The record, verified using data from a US National Oceanic and Atmospheric Administration satellite, beat the previous longest flash, 768 km (477 mi), documented in April 2020 in the same region.

"This new record clearly demonstrates the incredible power of the natural environment," Professor Randall Cerveny, the WMO's rapporteur on weather and climate extremes, said, noting that it is likely that even greater extremes still exist.

Lightning specialist Walt Lyons warned that the only lightning-safe locations are substantial buildings that have wiring and plumbing or a fully enclosed metal-topped vehicle.